1. Field of the Invention
The present invention relates to a radio communication equipment and a method for controlling a charge of the same, and more particularly to the radio communication equipment in which a charging circuit is embedded and the method for controlling a charge of the same.
2. Description of the Related Art
In recent years, a method for charging a battery of a portable telephone called a xe2x80x9cfloating charge methodxe2x80x9d is used in which the charging to the battery and/or power supply to loads of a radio section or a control section are performed by using a same circuit and same line. Because of this, a current flowing through a charging circuit is represented as a value of a current obtained by adding a value of a current applied to loads in the radio section or the control section to a charged current value.
In general, a current value indicating the completion of the charging of the portable telephone is set in accordance with a charging characteristic of a single battery or the charging characteristic appearing at the time of waiting for a call of the portable telephone. At this point, the current value indicating the completion of the charging is set by considering a consumed current as a load current value and the consumed current is at a level of several mA and is within specified limits that can be negligible.
On the other hand, though recent portable telephones have a backlight function used to light an LCD (Liquid Crystal Display) device and a key switch, the consumed current value at the time of using the backlight function, i.e., the load current value is very great compared with the current consumed while waiting for a call which is, for example, several tens of mA and therefore cannot be neglected when the current value indicating the completion of the charging is set. Usually, the backlight goes OFF within about 10 to 20 seconds. If the battery of portable telephones is charged with it connected to an in-car adapter, i.e., if the power is supplied through a cigarette lighter mounted in a motor vehicle, a user can select a mode in which the backlight is continuously lit. There are many cases where the backlight is continuously lit with the portable telephone connected to an in-car adapter. A night driver of a car selects the mode to continuously light the backlight to see a reading of a speedometer indicator or a tachometer. Moreover, such a selection is made, because, if the backlight goes OFF within about 10 to 20 seconds, the frequency of the lighting operation increases which may cause frequent traffic accidents or because the power supply from a cigarette lighter in a car eliminates the need for a concern for an increase in current consumption. However, if the user selects the continuous lighting mode at the time of charging and continues to light the backlight, the load current required for activating the backlight function increases, causing an increase of current flowing through the charging circuit. The charging is complete when a value of the current flowing through the charging circuit reaches the current value indicating the completion of the charging. However, if the load current required for activating the backlight function increases, a problem arises that there is a case where the charging is complete before the value of the current flowing through the charging circuit reaches the set current value indicating the completion of the charging.
The above problem is further described by referring to FIGS. 5A and 5B. FIG. 5A is a diagram showing a change of a charging voltage (i.e., charging characteristic) at the time of charging a conventional portable telephone and FIG. 5B is a diagram showing a change of a charging current (i.e., charging characteristic) at the time of charging the conventional portable telephone. In FIGS. 5A and 5B, the charging characteristic appearing when the backlight function is continuously used at the time of charging is shown by a full line and the charging characteristic appearing when the backlight function is not used at the time of charging is shown by a dotted line.
As shown in FIG. 5A, when the backlight function is not used at the time of charging (see the dotted line), the charging is started at time 0 and the charging is performed at a specified voltage VCHG, for example, at 4.1V at time T1 and, thereafter at a constant voltage. When the charging is complete at time T3, the charging voltage decreases. As shown in FIG. 5B, the charging is performed from time 0 to T1 at a constant current, for example, 500 mA and thereafter the charging is performed at the constant voltage, resulting in a decrease of the current. Then, when the charging current reaches a constant current ICUT1, for example, 50 mA, the charging is complete.
On the other hand, as shown in FIG. 5A, when the backlight function is used at the time of charging (see the solid line), the charging is started at time 0 and the charging voltage reaches a specified voltage VCHG at time T2 and thereafter the charging is performed at a constant voltage. Furthermore, as shown in FIG. 5B, the charging is performed from time 0 to T2 at a constant current ICHG and thereafter the charging is performed at the constant voltage, resulting in a decrease of the current.
However, in the portable telephone as described above, since the load current required for activating the backlight function flows continuously, the charging current, after having decreased, does not reach the current value ICUT1 indicating the completion of the charging. This causes a problem in that the charging is not normally complete. Another problem is that, because the charging is continued at the constant voltage VCHG, a battery is deteriorated.
To solve this problem, an idea is reported that the current value indicating the completion of the charging is set to a high value. However, in this case, though the charging is complete when the backlight function is continuously used, the charging is halfway complete when the charging is performed without the use of the backlight, causing charging capacity to be exhausted.
In view of the above, it is an object of the present invention to provide radio communication equipment which is capable of reliably completing a charge of a battery at a proper charging capacity and without causing deterioration of the battery regardless of whether or not a backlight function is continuously used at a time of charging.
According to a first embodiment of the present invention, there is provided radio communication equipment including:
displaying means for displaying various information;
operating means composed of keys;
lighting means for lighting the displaying means or the operating means;
current detecting means for detecting a charging current used for charging a battery;
judging means for judging whether the lighting means is turned ON or not;
setting means for a charging completion current value based on judged results obtained from the judging means; and
charging completing means for completing the charge when the charging current reaches the charging completion current set by the setting means.
In the foregoing, a preferable mode is one that wherein includes:
charging completion detecting means for detecting that the charging current has reached a charging completion current value set by the setting means;
battery voltage detecting means for detecting voltages of the battery;
switching means for switching a mode to charging of the battery; and
charging control means for controlling the switching means based on detected results obtained from the current detecting means, the charging completion detecting means and the battery voltage detecting means.
Also, a preferable mode is one wherein the setting means, when the lighting means is turned OFF, is used to set a first charging completion current value and, when the lighting means is turned ON, to set a second charging completion value which is larger than the first charging completion current value.
Also, a preferable mode is one wherein the second charging completion current value is a value obtained by adding load current values of the lighting means to the first charging completion current value.
Also, a preferable mode is one that wherein has outputting means for outputting a control signal to turn the lighting means ON/OFF based on operations of the operating means and wherein the judging means is used to judge whether the lighting means is turned ON or not based on the control signal.
According to a second aspect of the present invention, there is provided radio communication equipment including:
displaying means for displaying various information;
operating means composed of keys; and
whereby a charging completion current value is set based on whether the displaying means or the operating means is lit or not and charging is made complete when a charging current value to charge a battery reaches the set charging completion current value.
In the foregoing, it is preferable that the radio communication equipment is a portable telephone or a like.
According to a third aspect of the present invention, there is provided a method for controlling a charge of radio communication equipment including:
a step of starting the charge;
a step of judging whether a lighting circuit is turned ON;
a step of setting a charging completion current value based on judged results obtained from the judging step;
a step of detecting a charging current; and
a step of completing the charging when the charging current reaches the charging completion current value.
In the foregoing, a preferable mode is one wherein setting step includes a step of setting a first charging completion current value when the lighting circuit is turned OFF, and of setting a second charging completion current value that is larger than the first charging completion current value when the lighting circuit is turned ON and wherein the charging completion step includes a step of completing the charging when the charging current reaches the first and second charging completion current values based on the judged results.